<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        function vacancies () {
            let remain = +prompt('请输入银行卡余额')
            let mess = +prompt('请输入当月食宿消费金额')
            let life = +prompt('请输入当月生活消费金额')
            let surplus = remain - mess -life
            document.write(`银行卡中剩余${surplus}元`)
            return surplus
        }

        vacancies()
    </script>
</body>
</html>